From e5be12952ae9f4fd0874a8fb4e2f01414585b526 Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:38 +0000 Subject: [PATCH 01/18] mingw: don't call `GetFileAttributes()` twice in `mingw_lstat()` The Win32 API function `GetFileAttributes()` cannot handle paths with trailing dir separators. The current `mingw_stat()`/`mingw_lstat()` implementation calls `GetFileAttributes()` twice if the path has trailing slashes (first with the original path that was passed as function parameter, and and a second time with a path copy with trailing '/' removed). With the conversion to wide Unicode, we get the length of the path for free, and also have a (wide char) buffer that can be modified. This makes it easy to avoid that extraneous Win32 API call. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 48 ++++++++++++------------------------------------ 1 file changed, 12 insertions(+), 36 deletions(-) diff --git a/compat/mingw.c b/compat/mingw.c index cf4f3c92e7..f5a0fe3325 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -928,9 +928,18 @@ static int do_lstat(int follow, const char *file_name, struct stat *buf) { WIN32_FILE_ATTRIBUTE_DATA fdata; wchar_t wfilename[MAX_PATH]; - if (xutftowcs_path(wfilename, file_name) < 0) + int wlen = xutftowcs_path(wfilename, file_name); + if (wlen < 0) return -1; + /* strip trailing '/', or GetFileAttributes will fail */ + while (wlen && is_dir_sep(wfilename[wlen - 1])) + wfilename[--wlen] = 0; + if (!wlen) { + errno = ENOENT; + return -1; + } + if (GetFileAttributesExW(wfilename, GetFileExInfoStandard, &fdata)) { buf->st_ino = 0; buf->st_gid = 0; @@ -990,39 +999,6 @@ static int do_lstat(int follow, const char *file_name, struct stat *buf) return -1; } -/* We provide our own lstat/fstat functions, since the provided - * lstat/fstat functions are so slow. These stat functions are - * tailored for Git's usage (read: fast), and are not meant to be - * complete. Note that Git stat()s are redirected to mingw_lstat() - * too, since Windows doesn't really handle symlinks that well. - */ -static int do_stat_internal(int follow, const char *file_name, struct stat *buf) -{ - size_t namelen; - char alt_name[PATH_MAX]; - - if (!do_lstat(follow, file_name, buf)) - return 0; - - /* if file_name ended in a '/', Windows returned ENOENT; - * try again without trailing slashes - */ - if (errno != ENOENT) - return -1; - - namelen = strlen(file_name); - if (namelen && file_name[namelen-1] != '/') - return -1; - while (namelen && file_name[namelen-1] == '/') - --namelen; - if (!namelen || namelen >= PATH_MAX) - return -1; - - memcpy(alt_name, file_name, namelen); - alt_name[namelen] = 0; - return do_lstat(follow, alt_name, buf); -} - static int get_file_info_by_handle(HANDLE hnd, struct stat *buf) { BY_HANDLE_FILE_INFORMATION fdata; @@ -1048,11 +1024,11 @@ static int get_file_info_by_handle(HANDLE hnd, struct stat *buf) int mingw_lstat(const char *file_name, struct stat *buf) { - return do_stat_internal(0, file_name, buf); + return do_lstat(0, file_name, buf); } int mingw_stat(const char *file_name, struct stat *buf) { - return do_stat_internal(1, file_name, buf); + return do_lstat(1, file_name, buf); } int mingw_fstat(int fd, struct stat *buf) From 25866d0c501c5a28082f21f627dd9c015772209e Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:39 +0000 Subject: [PATCH 02/18] mingw: implement `stat()` with symlink support With respect to symlinks, the current `mingw_stat()` implementation is almost identical to `mingw_lstat()`: except for the file type (`st_mode & S_IFMT`), it returns information about the link rather than the target. Implement `mingw_stat()` by opening the file handle requesting minimal permissions, and then calling `GetFileInformationByHandle()` on it. This way, all links are resolved by the Windows file system layer. If symlinks are disabled, use `mingw_lstat()` as before, but fail with `ELOOP` if a symlink would have to be resolved. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/compat/mingw.c b/compat/mingw.c index f5a0fe3325..59afd69686 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -1026,9 +1026,26 @@ int mingw_lstat(const char *file_name, struct stat *buf) { return do_lstat(0, file_name, buf); } + int mingw_stat(const char *file_name, struct stat *buf) { - return do_lstat(1, file_name, buf); + wchar_t wfile_name[MAX_PATH]; + HANDLE hnd; + int result; + + /* open the file and let Windows resolve the links */ + if (xutftowcs_path(wfile_name, file_name) < 0) + return -1; + hnd = CreateFileW(wfile_name, 0, + FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL, + OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL); + if (hnd == INVALID_HANDLE_VALUE) { + errno = err_win_to_posix(GetLastError()); + return -1; + } + result = get_file_info_by_handle(hnd, buf); + CloseHandle(hnd); + return result; } int mingw_fstat(int fd, struct stat *buf) From b2d9214455efae880bfffe6ac787e2a4b982fecb Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:40 +0000 Subject: [PATCH 03/18] mingw: drop the separate `do_lstat()` function With the new `mingw_stat()` implementation, `do_lstat()` is only called from `mingw_lstat()` (with the function parameter `follow == 0`). Remove the extra function and the old `mingw_stat()`-specific (`follow == 1`) logic. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 22 ++-------------------- 1 file changed, 2 insertions(+), 20 deletions(-) diff --git a/compat/mingw.c b/compat/mingw.c index 59afd69686..ec6c2801d3 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -917,14 +917,7 @@ static int has_valid_directory_prefix(wchar_t *wfilename) return 1; } -/* We keep the do_lstat code in a separate function to avoid recursion. - * When a path ends with a slash, the stat will fail with ENOENT. In - * this case, we strip the trailing slashes and stat again. - * - * If follow is true then act like stat() and report on the link - * target. Otherwise report on the link itself. - */ -static int do_lstat(int follow, const char *file_name, struct stat *buf) +int mingw_lstat(const char *file_name, struct stat *buf) { WIN32_FILE_ATTRIBUTE_DATA fdata; wchar_t wfilename[MAX_PATH]; @@ -958,13 +951,7 @@ static int do_lstat(int follow, const char *file_name, struct stat *buf) if (handle != INVALID_HANDLE_VALUE) { if ((findbuf.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) && (findbuf.dwReserved0 == IO_REPARSE_TAG_SYMLINK)) { - if (follow) { - char buffer[MAXIMUM_REPARSE_DATA_BUFFER_SIZE]; - buf->st_size = readlink(file_name, buffer, MAXIMUM_REPARSE_DATA_BUFFER_SIZE); - } else { - buf->st_mode = S_IFLNK; - } - buf->st_mode |= S_IREAD; + buf->st_mode = S_IFLNK | S_IREAD; if (!(findbuf.dwFileAttributes & FILE_ATTRIBUTE_READONLY)) buf->st_mode |= S_IWRITE; } @@ -1022,11 +1009,6 @@ static int get_file_info_by_handle(HANDLE hnd, struct stat *buf) return 0; } -int mingw_lstat(const char *file_name, struct stat *buf) -{ - return do_lstat(0, file_name, buf); -} - int mingw_stat(const char *file_name, struct stat *buf) { wchar_t wfile_name[MAX_PATH]; From 8895855a4477c788b7a040d876978a7a6e18421a Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:41 +0000 Subject: [PATCH 04/18] mingw: let `mingw_lstat()` error early upon problems with reparse points When obtaining lstat information for reparse points, we need to call `FindFirstFile()` in addition to `GetFileInformationEx()` to obtain the type of the reparse point (symlink, mount point etc.). However, currently there is no error handling whatsoever if `FindFirstFile()` fails. Call `FindFirstFile()` before modifying the `stat *buf` output parameter and error out if the call fails. Note: The `FindFirstFile()` return value includes all the data that we get from `GetFileAttributesEx()`, so we could replace `GetFileAttributesEx()` with `FindFirstFile()`. We don't do that because `GetFileAttributesEx()` is about twice as fast for single files. I.e. we only pay the extra cost of calling `FindFirstFile()` in the rare case that we encounter a reparse point. Please also note that the indentation the remaining reparse point code changed, and hence the best way to look at this diff is with `--color-moved -w`. That code was _not_ moved because a subsequent commit will move it to an altogether different function, anyway. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/compat/mingw.c b/compat/mingw.c index ec6c2801d3..23a926c7d1 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -920,6 +920,7 @@ static int has_valid_directory_prefix(wchar_t *wfilename) int mingw_lstat(const char *file_name, struct stat *buf) { WIN32_FILE_ATTRIBUTE_DATA fdata; + WIN32_FIND_DATAW findbuf = { 0 }; wchar_t wfilename[MAX_PATH]; int wlen = xutftowcs_path(wfilename, file_name); if (wlen < 0) @@ -934,6 +935,13 @@ int mingw_lstat(const char *file_name, struct stat *buf) } if (GetFileAttributesExW(wfilename, GetFileExInfoStandard, &fdata)) { + /* for reparse points, use FindFirstFile to get the reparse tag */ + if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) { + HANDLE handle = FindFirstFileW(wfilename, &findbuf); + if (handle == INVALID_HANDLE_VALUE) + goto error; + FindClose(handle); + } buf->st_ino = 0; buf->st_gid = 0; buf->st_uid = 0; @@ -946,20 +954,16 @@ int mingw_lstat(const char *file_name, struct stat *buf) filetime_to_timespec(&(fdata.ftLastWriteTime), &(buf->st_mtim)); filetime_to_timespec(&(fdata.ftCreationTime), &(buf->st_ctim)); if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) { - WIN32_FIND_DATAW findbuf; - HANDLE handle = FindFirstFileW(wfilename, &findbuf); - if (handle != INVALID_HANDLE_VALUE) { - if ((findbuf.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) && - (findbuf.dwReserved0 == IO_REPARSE_TAG_SYMLINK)) { - buf->st_mode = S_IFLNK | S_IREAD; - if (!(findbuf.dwFileAttributes & FILE_ATTRIBUTE_READONLY)) - buf->st_mode |= S_IWRITE; - } - FindClose(handle); + if ((findbuf.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) && + (findbuf.dwReserved0 == IO_REPARSE_TAG_SYMLINK)) { + buf->st_mode = S_IFLNK | S_IREAD; + if (!(findbuf.dwFileAttributes & FILE_ATTRIBUTE_READONLY)) + buf->st_mode |= S_IWRITE; } } return 0; } +error: switch (GetLastError()) { case ERROR_ACCESS_DENIED: case ERROR_SHARING_VIOLATION: From 98e2eaf426b24871418b7e4c8312764f846c7cdf Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:42 +0000 Subject: [PATCH 05/18] mingw: teach dirent about symlinks Move the `S_IFLNK` detection to `file_attr_to_st_mode()`. Implement `DT_LNK` detection in dirent.c's `readdir()` function. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 13 +++---------- compat/win32.h | 6 ++++-- compat/win32/dirent.c | 5 ++++- 3 files changed, 11 insertions(+), 13 deletions(-) diff --git a/compat/mingw.c b/compat/mingw.c index 23a926c7d1..a3a48db581 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -946,21 +946,14 @@ int mingw_lstat(const char *file_name, struct stat *buf) buf->st_gid = 0; buf->st_uid = 0; buf->st_nlink = 1; - buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes); + buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes, + findbuf.dwReserved0); buf->st_size = fdata.nFileSizeLow | (((off_t)fdata.nFileSizeHigh)<<32); buf->st_dev = buf->st_rdev = 0; /* not used by Git */ filetime_to_timespec(&(fdata.ftLastAccessTime), &(buf->st_atim)); filetime_to_timespec(&(fdata.ftLastWriteTime), &(buf->st_mtim)); filetime_to_timespec(&(fdata.ftCreationTime), &(buf->st_ctim)); - if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) { - if ((findbuf.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) && - (findbuf.dwReserved0 == IO_REPARSE_TAG_SYMLINK)) { - buf->st_mode = S_IFLNK | S_IREAD; - if (!(findbuf.dwFileAttributes & FILE_ATTRIBUTE_READONLY)) - buf->st_mode |= S_IWRITE; - } - } return 0; } error: @@ -1003,7 +996,7 @@ static int get_file_info_by_handle(HANDLE hnd, struct stat *buf) buf->st_gid = 0; buf->st_uid = 0; buf->st_nlink = 1; - buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes); + buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes, 0); buf->st_size = fdata.nFileSizeLow | (((off_t)fdata.nFileSizeHigh)<<32); buf->st_dev = buf->st_rdev = 0; /* not used by Git */ diff --git a/compat/win32.h b/compat/win32.h index a97e880757..671bcc81f9 100644 --- a/compat/win32.h +++ b/compat/win32.h @@ -6,10 +6,12 @@ #include #endif -static inline int file_attr_to_st_mode (DWORD attr) +static inline int file_attr_to_st_mode (DWORD attr, DWORD tag) { int fMode = S_IREAD; - if (attr & FILE_ATTRIBUTE_DIRECTORY) + if ((attr & FILE_ATTRIBUTE_REPARSE_POINT) && tag == IO_REPARSE_TAG_SYMLINK) + fMode |= S_IFLNK; + else if (attr & FILE_ATTRIBUTE_DIRECTORY) fMode |= S_IFDIR; else fMode |= S_IFREG; diff --git a/compat/win32/dirent.c b/compat/win32/dirent.c index 52420ec7d4..24ee9b814d 100644 --- a/compat/win32/dirent.c +++ b/compat/win32/dirent.c @@ -12,7 +12,10 @@ static inline void finddata2dirent(struct dirent *ent, WIN32_FIND_DATAW *fdata) xwcstoutf(ent->d_name, fdata->cFileName, sizeof(ent->d_name)); /* Set file type, based on WIN32_FIND_DATA */ - if (fdata->dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) + if ((fdata->dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) + && fdata->dwReserved0 == IO_REPARSE_TAG_SYMLINK) + ent->d_type = DT_LNK; + else if (fdata->dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) ent->d_type = DT_DIR; else ent->d_type = DT_REG; From c08814a5c41064e2abd5ce999dbf905173be03e2 Mon Sep 17 00:00:00 2001 From: Bill Zissimopoulos Date: Wed, 17 Dec 2025 14:08:43 +0000 Subject: [PATCH 06/18] mingw: compute the correct size for symlinks in `mingw_lstat()` POSIX specifies that upon successful return from `lstat()`: "the value of the st_size member shall be set to the length of the pathname contained in the symbolic link not including any terminating null byte". Git typically doesn't trust the `stat.st_size` member of symlinks (e.g. see `strbuf_readlink()`). Therefore, it is tempting to save on the extra overhead of opening and reading the reparse point merely to calculate the exact size of the link target. This is, in fact, what Git for Windows did, from May 2015 to May 2020. At least almost: some functions take shortcuts if `st_size` is 0 (e.g. `diff_populate_filespec()`), hence Git for Windows hard-coded the length of all symlinks to MAX_PATH. This did cause problems, though, specifically in Git repositories that were also accessed by Git for Cygwin or Git for WSL. For example, doing `git reset --hard` using Git for Windows would update the size of symlinks in the index to be MAX_PATH; at a later time Git for Cygwin or Git for WSL would find that symlinks have changed size during `git status` and update the index. And then Git for Windows would think that the index needs to be updated. Even if the symlinks did not, in fact, change. To avoid that, the correct size must be determined. Signed-off-by: Bill Zissimopoulos Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 114 ++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 104 insertions(+), 10 deletions(-) diff --git a/compat/mingw.c b/compat/mingw.c index a3a48db581..c7571951dc 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -21,6 +21,7 @@ #define SECURITY_WIN32 #include #include +#include #include #define STATUS_DELETE_PENDING ((NTSTATUS) 0xC0000056) @@ -917,10 +918,102 @@ static int has_valid_directory_prefix(wchar_t *wfilename) return 1; } +#ifndef _WINNT_H +/* + * The REPARSE_DATA_BUFFER structure is defined in the Windows DDK (in + * ntifs.h) and in MSYS1's winnt.h (which defines _WINNT_H). So define + * it ourselves if we are on MSYS2 (whose winnt.h defines _WINNT_). + */ +typedef struct _REPARSE_DATA_BUFFER { + DWORD ReparseTag; + WORD ReparseDataLength; + WORD Reserved; +#ifndef _MSC_VER + _ANONYMOUS_UNION +#endif + union { + struct { + WORD SubstituteNameOffset; + WORD SubstituteNameLength; + WORD PrintNameOffset; + WORD PrintNameLength; + ULONG Flags; + WCHAR PathBuffer[1]; + } SymbolicLinkReparseBuffer; + struct { + WORD SubstituteNameOffset; + WORD SubstituteNameLength; + WORD PrintNameOffset; + WORD PrintNameLength; + WCHAR PathBuffer[1]; + } MountPointReparseBuffer; + struct { + BYTE DataBuffer[1]; + } GenericReparseBuffer; + } DUMMYUNIONNAME; +} REPARSE_DATA_BUFFER, *PREPARSE_DATA_BUFFER; +#endif + +static int read_reparse_point(const WCHAR *wpath, BOOL fail_on_unknown_tag, + char *tmpbuf, int *plen, DWORD *ptag) +{ + HANDLE handle; + WCHAR *wbuf; + REPARSE_DATA_BUFFER *b = alloca(MAXIMUM_REPARSE_DATA_BUFFER_SIZE); + DWORD dummy; + + /* read reparse point data */ + handle = CreateFileW(wpath, 0, + FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL, + OPEN_EXISTING, + FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT, NULL); + if (handle == INVALID_HANDLE_VALUE) { + errno = err_win_to_posix(GetLastError()); + return -1; + } + if (!DeviceIoControl(handle, FSCTL_GET_REPARSE_POINT, NULL, 0, b, + MAXIMUM_REPARSE_DATA_BUFFER_SIZE, &dummy, NULL)) { + errno = err_win_to_posix(GetLastError()); + CloseHandle(handle); + return -1; + } + CloseHandle(handle); + + /* get target path for symlinks or mount points (aka 'junctions') */ + switch ((*ptag = b->ReparseTag)) { + case IO_REPARSE_TAG_SYMLINK: + wbuf = (WCHAR*) (((char*) b->SymbolicLinkReparseBuffer.PathBuffer) + + b->SymbolicLinkReparseBuffer.SubstituteNameOffset); + *(WCHAR*) (((char*) wbuf) + + b->SymbolicLinkReparseBuffer.SubstituteNameLength) = 0; + break; + case IO_REPARSE_TAG_MOUNT_POINT: + wbuf = (WCHAR*) (((char*) b->MountPointReparseBuffer.PathBuffer) + + b->MountPointReparseBuffer.SubstituteNameOffset); + *(WCHAR*) (((char*) wbuf) + + b->MountPointReparseBuffer.SubstituteNameLength) = 0; + break; + default: + if (fail_on_unknown_tag) { + errno = EINVAL; + return -1; + } else { + *plen = MAX_PATH; + return 0; + } + } + + if ((*plen = + xwcstoutf(tmpbuf, normalize_ntpath(wbuf), MAX_PATH)) < 0) + return -1; + return 0; +} + int mingw_lstat(const char *file_name, struct stat *buf) { WIN32_FILE_ATTRIBUTE_DATA fdata; - WIN32_FIND_DATAW findbuf = { 0 }; + DWORD reparse_tag = 0; + int link_len = 0; wchar_t wfilename[MAX_PATH]; int wlen = xutftowcs_path(wfilename, file_name); if (wlen < 0) @@ -935,28 +1028,29 @@ int mingw_lstat(const char *file_name, struct stat *buf) } if (GetFileAttributesExW(wfilename, GetFileExInfoStandard, &fdata)) { - /* for reparse points, use FindFirstFile to get the reparse tag */ + /* for reparse points, get the link tag and length */ if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) { - HANDLE handle = FindFirstFileW(wfilename, &findbuf); - if (handle == INVALID_HANDLE_VALUE) - goto error; - FindClose(handle); + char tmpbuf[MAX_PATH]; + + if (read_reparse_point(wfilename, FALSE, tmpbuf, + &link_len, &reparse_tag) < 0) + return -1; } buf->st_ino = 0; buf->st_gid = 0; buf->st_uid = 0; buf->st_nlink = 1; buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes, - findbuf.dwReserved0); - buf->st_size = fdata.nFileSizeLow | - (((off_t)fdata.nFileSizeHigh)<<32); + reparse_tag); + buf->st_size = S_ISLNK(buf->st_mode) ? link_len : + fdata.nFileSizeLow | (((off_t) fdata.nFileSizeHigh) << 32); buf->st_dev = buf->st_rdev = 0; /* not used by Git */ filetime_to_timespec(&(fdata.ftLastAccessTime), &(buf->st_atim)); filetime_to_timespec(&(fdata.ftLastWriteTime), &(buf->st_mtim)); filetime_to_timespec(&(fdata.ftCreationTime), &(buf->st_ctim)); return 0; } -error: + switch (GetLastError()) { case ERROR_ACCESS_DENIED: case ERROR_SHARING_VIOLATION: From fc27de047a688449be828f4e59a5a8c70b3aa49e Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:44 +0000 Subject: [PATCH 07/18] mingw: factor out the retry logic In several places, Git's Windows-specific code follows the pattern where it tries to perform an operation, and retries several times when that operation fails, sleeping an increasing amount of time, before finally giving up and asking the user whether to rety (after, say, closing an editor that held a handle to a file, preventing the operation from succeeding). This logic is a bit hard to use, and inconsistent: `mingw_unlink()` and `mingw_rmdir()` duplicate the code to retry, and both of them do so incompletely. They also do not restore `errno` if the user answers 'no'. Introduce a `retry_ask_yes_no()` helper function that handles retry with small delay, asking the user, and restoring `errno`. Note that in `mingw_unlink()`, we include the `_wchmod()` call in the retry loop (which may fail if the file is locked exclusively). In `mingw_rmdir()`, we include special error handling in the retry loop. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 104 ++++++++++++++++++++++--------------------------- 1 file changed, 46 insertions(+), 58 deletions(-) diff --git a/compat/mingw.c b/compat/mingw.c index c7571951dc..26e64c6a5a 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -28,8 +28,6 @@ #define HCAST(type, handle) ((type)(intptr_t)handle) -static const int delay[] = { 0, 1, 10, 20, 40 }; - void open_in_gdb(void) { static struct child_process cp = CHILD_PROCESS_INIT; @@ -205,15 +203,12 @@ static int read_yes_no_answer(void) return -1; } -static int ask_yes_no_if_possible(const char *format, ...) +static int ask_yes_no_if_possible(const char *format, va_list args) { char question[4096]; const char *retry_hook; - va_list args; - va_start(args, format); vsnprintf(question, sizeof(question), format, args); - va_end(args); retry_hook = mingw_getenv("GIT_ASK_YESNO"); if (retry_hook) { @@ -238,6 +233,31 @@ static int ask_yes_no_if_possible(const char *format, ...) } } +static int retry_ask_yes_no(int *tries, const char *format, ...) +{ + static const int delay[] = { 0, 1, 10, 20, 40 }; + va_list args; + int result, saved_errno = errno; + + if ((*tries) < ARRAY_SIZE(delay)) { + /* + * We assume that some other process had the file open at the wrong + * moment and retry. In order to give the other process a higher + * chance to complete its operation, we give up our time slice now. + * If we have to retry again, we do sleep a bit. + */ + Sleep(delay[*tries]); + (*tries)++; + return 1; + } + + va_start(args, format); + result = ask_yes_no_if_possible(format, args); + va_end(args); + errno = saved_errno; + return result; +} + /* Windows only */ enum hide_dotfiles_type { HIDE_DOTFILES_FALSE = 0, @@ -298,7 +318,7 @@ static wchar_t *normalize_ntpath(wchar_t *wbuf) int mingw_unlink(const char *pathname, int handle_in_use_error) { - int ret, tries = 0; + int tries = 0; wchar_t wpathname[MAX_PATH]; if (xutftowcs_path(wpathname, pathname) < 0) return -1; @@ -306,29 +326,19 @@ int mingw_unlink(const char *pathname, int handle_in_use_error) if (DeleteFileW(wpathname)) return 0; - /* read-only files cannot be removed */ - _wchmod(wpathname, 0666); - while ((ret = _wunlink(wpathname)) == -1 && tries < ARRAY_SIZE(delay)) { + do { + /* read-only files cannot be removed */ + _wchmod(wpathname, 0666); + if (!_wunlink(wpathname)) + return 0; if (!is_file_in_use_error(GetLastError())) break; if (!handle_in_use_error) - return ret; + return -1; - /* - * We assume that some other process had the source or - * destination file open at the wrong moment and retry. - * In order to give the other process a higher chance to - * complete its operation, we give up our time slice now. - * If we have to retry again, we do sleep a bit. - */ - Sleep(delay[tries]); - tries++; - } - while (ret == -1 && is_file_in_use_error(GetLastError()) && - ask_yes_no_if_possible("Unlink of file '%s' failed. " - "Should I try again?", pathname)) - ret = _wunlink(wpathname); - return ret; + } while (retry_ask_yes_no(&tries, "Unlink of file '%s' failed. " + "Should I try again?", pathname)); + return -1; } static int is_dir_empty(const wchar_t *wpath) @@ -355,7 +365,7 @@ static int is_dir_empty(const wchar_t *wpath) int mingw_rmdir(const char *pathname) { - int ret, tries = 0; + int tries = 0; wchar_t wpathname[MAX_PATH]; struct stat st; @@ -381,7 +391,11 @@ int mingw_rmdir(const char *pathname) if (xutftowcs_path(wpathname, pathname) < 0) return -1; - while ((ret = _wrmdir(wpathname)) == -1 && tries < ARRAY_SIZE(delay)) { + do { + if (!_wrmdir(wpathname)) { + invalidate_lstat_cache(); + return 0; + } if (!is_file_in_use_error(GetLastError())) errno = err_win_to_posix(GetLastError()); if (errno != EACCES) @@ -390,23 +404,9 @@ int mingw_rmdir(const char *pathname) errno = ENOTEMPTY; break; } - /* - * We assume that some other process had the source or - * destination file open at the wrong moment and retry. - * In order to give the other process a higher chance to - * complete its operation, we give up our time slice now. - * If we have to retry again, we do sleep a bit. - */ - Sleep(delay[tries]); - tries++; - } - while (ret == -1 && errno == EACCES && is_file_in_use_error(GetLastError()) && - ask_yes_no_if_possible("Deletion of directory '%s' failed. " - "Should I try again?", pathname)) - ret = _wrmdir(wpathname); - if (!ret) - invalidate_lstat_cache(); - return ret; + } while (retry_ask_yes_no(&tries, "Deletion of directory '%s' failed. " + "Should I try again?", pathname)); + return -1; } static inline int needs_hiding(const char *path) @@ -2384,20 +2384,8 @@ repeat: SetFileAttributesW(wpnew, attrs); } } - if (tries < ARRAY_SIZE(delay) && gle == ERROR_ACCESS_DENIED) { - /* - * We assume that some other process had the source or - * destination file open at the wrong moment and retry. - * In order to give the other process a higher chance to - * complete its operation, we give up our time slice now. - * If we have to retry again, we do sleep a bit. - */ - Sleep(delay[tries]); - tries++; - goto repeat; - } if (gle == ERROR_ACCESS_DENIED && - ask_yes_no_if_possible("Rename from '%s' to '%s' failed. " + retry_ask_yes_no(&tries, "Rename from '%s' to '%s' failed. " "Should I try again?", pold, pnew)) goto repeat; From 988ba47d7936d8438bb01200c320afc3635e2d37 Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:45 +0000 Subject: [PATCH 08/18] mingw: change default of `core.symlinks` to false Symlinks on Windows don't work the same way as on Unix systems. For example, there are different types of symlinks for directories and files, and unless using a recent-ish Windows version in Developer Mode, creating symlinks requires administrative privileges. By default, disable symlink support on Windows. That is, users explicitly have to enable it with `git config [--system|--global] core.symlinks true`; For convenience, `git init` (and `git clone`) will perform a test whether the current setup allows creating symlinks and will configure that setting in the repository config. The test suite ignores system / global config files. Allow testing *with* symlink support by checking if native symlinks are enabled in MSYS2 (via setting the special environment variable `MSYS=winsymlinks:nativestrict` to ask the MSYS2 runtime to enable creating symlinks). Note: This assumes that Git's test suite is run in MSYS2's Bash, which is true for the time being (an experiment to switch to BusyBox-w32 failed due to the experimental nature of BusyBox-w32). Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/compat/mingw.c b/compat/mingw.c index 26e64c6a5a..0fe00a5b70 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -2862,6 +2862,15 @@ static void setup_windows_environment(void) if (!tmp && (tmp = getenv("USERPROFILE"))) setenv("HOME", tmp, 1); } + + /* + * Change 'core.symlinks' default to false, unless native symlinks are + * enabled in MSys2 (via 'MSYS=winsymlinks:nativestrict'). Thus we can + * run the test suite (which doesn't obey config files) with or without + * symlink support. + */ + if (!(tmp = getenv("MSYS")) || !strstr(tmp, "winsymlinks:nativestrict")) + has_symlinks = 0; } static void get_current_user_sid(PSID *sid, HANDLE *linked_token) From 761d9427bcb8c54bb4b15d317465349203eb5935 Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:46 +0000 Subject: [PATCH 09/18] mingw: add symlink-specific error codes The Win32 API calls do not set `errno`; Instead, error codes for failed operations must be obtained via the `GetLastError()` function. Git would not know what to do with those error values, though, which is why Git's Windows compatibility layer translates them to `errno` values. Let's handle a couple of symlink-related error codes that will become relevant with the upcoming support for symlinks on Windows. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/compat/mingw.c b/compat/mingw.c index 0fe00a5b70..0e8807196f 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -102,6 +102,7 @@ int err_win_to_posix(DWORD winerr) case ERROR_INVALID_PARAMETER: error = EINVAL; break; case ERROR_INVALID_PASSWORD: error = EPERM; break; case ERROR_INVALID_PRIMARY_GROUP: error = EINVAL; break; + case ERROR_INVALID_REPARSE_DATA: error = EINVAL; break; case ERROR_INVALID_SIGNAL_NUMBER: error = EINVAL; break; case ERROR_INVALID_TARGET_HANDLE: error = EIO; break; case ERROR_INVALID_WORKSTATION: error = EACCES; break; @@ -116,6 +117,7 @@ int err_win_to_posix(DWORD winerr) case ERROR_NEGATIVE_SEEK: error = ESPIPE; break; case ERROR_NOACCESS: error = EFAULT; break; case ERROR_NONE_MAPPED: error = EINVAL; break; + case ERROR_NOT_A_REPARSE_POINT: error = EINVAL; break; case ERROR_NOT_ENOUGH_MEMORY: error = ENOMEM; break; case ERROR_NOT_READY: error = EAGAIN; break; case ERROR_NOT_SAME_DEVICE: error = EXDEV; break; @@ -136,6 +138,9 @@ int err_win_to_posix(DWORD winerr) case ERROR_PIPE_NOT_CONNECTED: error = EPIPE; break; case ERROR_PRIVILEGE_NOT_HELD: error = EACCES; break; case ERROR_READ_FAULT: error = EIO; break; + case ERROR_REPARSE_ATTRIBUTE_CONFLICT: error = EINVAL; break; + case ERROR_REPARSE_TAG_INVALID: error = EINVAL; break; + case ERROR_REPARSE_TAG_MISMATCH: error = EINVAL; break; case ERROR_SEEK: error = EIO; break; case ERROR_SEEK_ON_DEVICE: error = ESPIPE; break; case ERROR_SHARING_BUFFER_EXCEEDED: error = ENFILE; break; From 47112d6f9671d2ed9e8034bf709442c279f53029 Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:47 +0000 Subject: [PATCH 10/18] mingw: handle symlinks to directories in `mingw_unlink()` The `_wunlink()` and `DeleteFileW()` functions refuse to delete symlinks to directories on Windows; The error code woutl be `ERROR_ACCESS_DENIED` in that case. Take that error code as an indicator that we need to try `_wrmdir()` as well. In the best case, it will remove a symlink. In the worst case, it will fail with the same error code again. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/compat/mingw.c b/compat/mingw.c index 0e8807196f..b1cc30d0f1 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -338,9 +338,16 @@ int mingw_unlink(const char *pathname, int handle_in_use_error) return 0; if (!is_file_in_use_error(GetLastError())) break; + /* + * _wunlink() / DeleteFileW() for directory symlinks fails with + * ERROR_ACCESS_DENIED (EACCES), so try _wrmdir() as well. This is the + * same error we get if a file is in use (already checked above). + */ + if (!_wrmdir(wpathname)) + return 0; + if (!handle_in_use_error) return -1; - } while (retry_ask_yes_no(&tries, "Unlink of file '%s' failed. " "Should I try again?", pathname)); return -1; From c4314a6aa8fbb9a00d6068135fe19b5637a6992a Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:48 +0000 Subject: [PATCH 11/18] mingw: support renaming symlinks Older MSVCRT's `_wrename()` function cannot rename symlinks over existing files: it returns success without doing anything. Newer MSVCR*.dll versions probably do not share this problem: according to CRT sources, they just call `MoveFileEx()` with the `MOVEFILE_COPY_ALLOWED` flag. Avoid the `_wrename()` call, and go with directly calling `MoveFileEx()`, with proper error handling of course. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 38 ++++++++++++++++---------------------- 1 file changed, 16 insertions(+), 22 deletions(-) diff --git a/compat/mingw.c b/compat/mingw.c index b1cc30d0f1..55f0bb478e 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -2275,7 +2275,7 @@ int mingw_accept(int sockfd1, struct sockaddr *sa, socklen_t *sz) int mingw_rename(const char *pold, const char *pnew) { static int supports_file_rename_info_ex = 1; - DWORD attrs, gle; + DWORD attrs = INVALID_FILE_ATTRIBUTES, gle; int tries = 0; wchar_t wpold[MAX_PATH], wpnew[MAX_PATH]; int wpnew_len; @@ -2286,15 +2286,6 @@ int mingw_rename(const char *pold, const char *pnew) if (wpnew_len < 0) return -1; - /* - * Try native rename() first to get errno right. - * It is based on MoveFile(), which cannot overwrite existing files. - */ - if (!_wrename(wpold, wpnew)) - return 0; - if (errno != EEXIST) - return -1; - repeat: if (supports_file_rename_info_ex) { /* @@ -2370,13 +2361,22 @@ repeat: * to retry. */ } else { - if (MoveFileExW(wpold, wpnew, MOVEFILE_REPLACE_EXISTING)) + if (MoveFileExW(wpold, wpnew, + MOVEFILE_REPLACE_EXISTING | MOVEFILE_COPY_ALLOWED)) return 0; gle = GetLastError(); } - /* TODO: translate more errors */ - if (gle == ERROR_ACCESS_DENIED && + /* revert file attributes on failure */ + if (attrs != INVALID_FILE_ATTRIBUTES) + SetFileAttributesW(wpnew, attrs); + + if (!is_file_in_use_error(gle)) { + errno = err_win_to_posix(gle); + return -1; + } + + if (attrs == INVALID_FILE_ATTRIBUTES && (attrs = GetFileAttributesW(wpnew)) != INVALID_FILE_ATTRIBUTES) { if (attrs & FILE_ATTRIBUTE_DIRECTORY) { DWORD attrsold = GetFileAttributesW(wpold); @@ -2388,16 +2388,10 @@ repeat: return -1; } if ((attrs & FILE_ATTRIBUTE_READONLY) && - SetFileAttributesW(wpnew, attrs & ~FILE_ATTRIBUTE_READONLY)) { - if (MoveFileExW(wpold, wpnew, MOVEFILE_REPLACE_EXISTING)) - return 0; - gle = GetLastError(); - /* revert file attributes on failure */ - SetFileAttributesW(wpnew, attrs); - } + SetFileAttributesW(wpnew, attrs & ~FILE_ATTRIBUTE_READONLY)) + goto repeat; } - if (gle == ERROR_ACCESS_DENIED && - retry_ask_yes_no(&tries, "Rename from '%s' to '%s' failed. " + if (retry_ask_yes_no(&tries, "Rename from '%s' to '%s' failed. " "Should I try again?", pold, pnew)) goto repeat; From 8a08d14d0537aa46f89c205c0f33130d9fbff648 Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:49 +0000 Subject: [PATCH 12/18] mingw: allow `mingw_chdir()` to change to symlink-resolved directories If symlinks are enabled, resolve all symlinks when changing directories, as required by POSIX. Note: Git's `real_path()` function bases its link resolution algorithm on this property of `chdir()`. Unfortunately, the current directory on Windows is limited to only MAX_PATH (260) characters. Therefore using symlinks and long paths in combination may be problematic. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/compat/mingw.c b/compat/mingw.c index 55f0bb478e..5d2a8c247c 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -866,9 +866,27 @@ int mingw_access(const char *filename, int mode) int mingw_chdir(const char *dirname) { wchar_t wdirname[MAX_PATH]; + if (xutftowcs_path(wdirname, dirname) < 0) return -1; - return _wchdir(wdirname); + + if (has_symlinks) { + HANDLE hnd = CreateFileW(wdirname, 0, + FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL, + OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL); + if (hnd == INVALID_HANDLE_VALUE) { + errno = err_win_to_posix(GetLastError()); + return -1; + } + if (!GetFinalPathNameByHandleW(hnd, wdirname, ARRAY_SIZE(wdirname), 0)) { + errno = err_win_to_posix(GetLastError()); + CloseHandle(hnd); + return -1; + } + CloseHandle(hnd); + } + + return _wchdir(normalize_ntpath(wdirname)); } int mingw_chmod(const char *filename, int mode) From 1977e5b9dee8b71f472ba10cfba851c686f6fada Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:50 +0000 Subject: [PATCH 13/18] mingw: implement `readlink()` Implement `readlink()` by reading NTFS reparse points via the `read_reparse_point()` function that was introduced earlier to determine the length of symlink targets. Works for symlinks and directory junctions. If symlinks are disabled, fail with `ENOSYS`. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw-posix.h | 3 +-- compat/mingw.c | 24 ++++++++++++++++++++++++ 2 files changed, 25 insertions(+), 2 deletions(-) diff --git a/compat/mingw-posix.h b/compat/mingw-posix.h index 0939feff27..896aa976b1 100644 --- a/compat/mingw-posix.h +++ b/compat/mingw-posix.h @@ -121,8 +121,6 @@ struct utsname { * trivial stubs */ -static inline int readlink(const char *path UNUSED, char *buf UNUSED, size_t bufsiz UNUSED) -{ errno = ENOSYS; return -1; } static inline int symlink(const char *oldpath UNUSED, const char *newpath UNUSED) { errno = ENOSYS; return -1; } static inline int fchmod(int fildes UNUSED, mode_t mode UNUSED) @@ -197,6 +195,7 @@ int setitimer(int type, struct itimerval *in, struct itimerval *out); int sigaction(int sig, struct sigaction *in, struct sigaction *out); int link(const char *oldpath, const char *newpath); int uname(struct utsname *buf); +int readlink(const char *path, char *buf, size_t bufsiz); /* * replacements of existing functions diff --git a/compat/mingw.c b/compat/mingw.c index 5d2a8c247c..b407a2ac07 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -2698,6 +2698,30 @@ int link(const char *oldpath, const char *newpath) return 0; } +int readlink(const char *path, char *buf, size_t bufsiz) +{ + WCHAR wpath[MAX_PATH]; + char tmpbuf[MAX_PATH]; + int len; + DWORD tag; + + if (xutftowcs_path(wpath, path) < 0) + return -1; + + if (read_reparse_point(wpath, TRUE, tmpbuf, &len, &tag) < 0) + return -1; + + /* + * Adapt to strange readlink() API: Copy up to bufsiz *bytes*, potentially + * cutting off a UTF-8 sequence. Insufficient bufsize is *not* a failure + * condition. There is no conversion function that produces invalid UTF-8, + * so convert to a (hopefully large enough) temporary buffer, then memcpy + * the requested number of bytes (including '\0' for robustness). + */ + memcpy(buf, tmpbuf, min(bufsiz, len + 1)); + return min(bufsiz, len); +} + pid_t waitpid(pid_t pid, int *status, int options) { HANDLE h = OpenProcess(SYNCHRONIZE | PROCESS_QUERY_INFORMATION, From 3aeb1cd126f338e23415885b3021c7f248f9ca0a Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:51 +0000 Subject: [PATCH 14/18] mingw: implement basic `symlink()` functionality (file symlinks only) Implement `symlink()`. This implementation always creates _file_ symlinks (remember: Windows discerns between symlinks pointing to directories and those pointing to files). Support for directory symlinks will be added in a subseqeuent commit. This implementation fails with `ENOSYS` if symlinks are disabled or unsupported. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw-posix.h | 3 +-- compat/mingw.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 29 insertions(+), 2 deletions(-) diff --git a/compat/mingw-posix.h b/compat/mingw-posix.h index 896aa976b1..2d989fd762 100644 --- a/compat/mingw-posix.h +++ b/compat/mingw-posix.h @@ -121,8 +121,6 @@ struct utsname { * trivial stubs */ -static inline int symlink(const char *oldpath UNUSED, const char *newpath UNUSED) -{ errno = ENOSYS; return -1; } static inline int fchmod(int fildes UNUSED, mode_t mode UNUSED) { errno = ENOSYS; return -1; } #ifndef __MINGW64_VERSION_MAJOR @@ -195,6 +193,7 @@ int setitimer(int type, struct itimerval *in, struct itimerval *out); int sigaction(int sig, struct sigaction *in, struct sigaction *out); int link(const char *oldpath, const char *newpath); int uname(struct utsname *buf); +int symlink(const char *target, const char *link); int readlink(const char *path, char *buf, size_t bufsiz); /* diff --git a/compat/mingw.c b/compat/mingw.c index b407a2ac07..8d366794c4 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -2698,6 +2698,34 @@ int link(const char *oldpath, const char *newpath) return 0; } +int symlink(const char *target, const char *link) +{ + wchar_t wtarget[MAX_PATH], wlink[MAX_PATH]; + int len; + + /* fail if symlinks are disabled or API is not supported (WinXP) */ + if (!has_symlinks) { + errno = ENOSYS; + return -1; + } + + if ((len = xutftowcs_path(wtarget, target)) < 0 + || xutftowcs_path(wlink, link) < 0) + return -1; + + /* convert target dir separators to backslashes */ + while (len--) + if (wtarget[len] == '/') + wtarget[len] = '\\'; + + /* create file symlink */ + if (!CreateSymbolicLinkW(wlink, wtarget, 0)) { + errno = err_win_to_posix(GetLastError()); + return -1; + } + return 0; +} + int readlink(const char *path, char *buf, size_t bufsiz) { WCHAR wpath[MAX_PATH]; From e81cbd184f7491809f4294df0e2d941a00dceaa5 Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Wed, 17 Dec 2025 14:08:52 +0000 Subject: [PATCH 15/18] mingw: add support for symlinks to directories Symlinks on Windows have a flag that indicates whether the target is a file or a directory. Symlinks of wrong type simply don't work. This even affects core Win32 APIs (e.g. `DeleteFile()` refuses to delete directory symlinks). However, `CreateFile()` with FILE_FLAG_BACKUP_SEMANTICS does work. Check the target type by first creating a tentative file symlink, opening it, and checking the type of the resulting handle. If it is a directory, recreate the symlink with the directory flag set. It is possible to create symlinks before the target exists (or in case of symlinks to symlinks: before the target type is known). If this happens, create a tentative file symlink and postpone the directory decision: keep a list of phantom symlinks to be processed whenever a new directory is created in `mingw_mkdir()`. Limitations: This algorithm may fail if a link target changes from file to directory or vice versa, or if the target directory is created in another process. It's the best Git can do, though. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 164 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 164 insertions(+) diff --git a/compat/mingw.c b/compat/mingw.c index 8d366794c4..59a32e454e 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -296,6 +296,131 @@ int mingw_core_config(const char *var, const char *value, return 0; } +static inline int is_wdir_sep(wchar_t wchar) +{ + return wchar == L'/' || wchar == L'\\'; +} + +static const wchar_t *make_relative_to(const wchar_t *path, + const wchar_t *relative_to, wchar_t *out, + size_t size) +{ + size_t i = wcslen(relative_to), len; + + /* Is `path` already absolute? */ + if (is_wdir_sep(path[0]) || + (iswalpha(path[0]) && path[1] == L':' && is_wdir_sep(path[2]))) + return path; + + while (i > 0 && !is_wdir_sep(relative_to[i - 1])) + i--; + + /* Is `relative_to` in the current directory? */ + if (!i) + return path; + + len = wcslen(path); + if (i + len + 1 > size) { + error("Could not make '%ls' relative to '%ls' (too large)", + path, relative_to); + return NULL; + } + + memcpy(out, relative_to, i * sizeof(wchar_t)); + wcscpy(out + i, path); + return out; +} + +enum phantom_symlink_result { + PHANTOM_SYMLINK_RETRY, + PHANTOM_SYMLINK_DONE, + PHANTOM_SYMLINK_DIRECTORY +}; + +/* + * Changes a file symlink to a directory symlink if the target exists and is a + * directory. + */ +static enum phantom_symlink_result +process_phantom_symlink(const wchar_t *wtarget, const wchar_t *wlink) +{ + HANDLE hnd; + BY_HANDLE_FILE_INFORMATION fdata; + wchar_t relative[MAX_PATH]; + const wchar_t *rel; + + /* check that wlink is still a file symlink */ + if ((GetFileAttributesW(wlink) + & (FILE_ATTRIBUTE_REPARSE_POINT | FILE_ATTRIBUTE_DIRECTORY)) + != FILE_ATTRIBUTE_REPARSE_POINT) + return PHANTOM_SYMLINK_DONE; + + /* make it relative, if necessary */ + rel = make_relative_to(wtarget, wlink, relative, ARRAY_SIZE(relative)); + if (!rel) + return PHANTOM_SYMLINK_DONE; + + /* let Windows resolve the link by opening it */ + hnd = CreateFileW(rel, 0, + FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL, + OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL); + if (hnd == INVALID_HANDLE_VALUE) { + errno = err_win_to_posix(GetLastError()); + return PHANTOM_SYMLINK_RETRY; + } + + if (!GetFileInformationByHandle(hnd, &fdata)) { + errno = err_win_to_posix(GetLastError()); + CloseHandle(hnd); + return PHANTOM_SYMLINK_RETRY; + } + CloseHandle(hnd); + + /* if target exists and is a file, we're done */ + if (!(fdata.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)) + return PHANTOM_SYMLINK_DONE; + + /* otherwise recreate the symlink with directory flag */ + if (DeleteFileW(wlink) && CreateSymbolicLinkW(wlink, wtarget, 1)) + return PHANTOM_SYMLINK_DIRECTORY; + + errno = err_win_to_posix(GetLastError()); + return PHANTOM_SYMLINK_RETRY; +} + +/* keep track of newly created symlinks to non-existing targets */ +struct phantom_symlink_info { + struct phantom_symlink_info *next; + wchar_t *wlink; + wchar_t *wtarget; +}; + +static struct phantom_symlink_info *phantom_symlinks = NULL; +static CRITICAL_SECTION phantom_symlinks_cs; + +static void process_phantom_symlinks(void) +{ + struct phantom_symlink_info *current, **psi; + EnterCriticalSection(&phantom_symlinks_cs); + /* process phantom symlinks list */ + psi = &phantom_symlinks; + while ((current = *psi)) { + enum phantom_symlink_result result = process_phantom_symlink( + current->wtarget, current->wlink); + if (result == PHANTOM_SYMLINK_RETRY) { + psi = ¤t->next; + } else { + /* symlink was processed, remove from list */ + *psi = current->next; + free(current); + /* if symlink was a directory, start over */ + if (result == PHANTOM_SYMLINK_DIRECTORY) + psi = &phantom_symlinks; + } + } + LeaveCriticalSection(&phantom_symlinks_cs); +} + /* Normalizes NT paths as returned by some low-level APIs. */ static wchar_t *normalize_ntpath(wchar_t *wbuf) { @@ -479,6 +604,8 @@ int mingw_mkdir(const char *path, int mode UNUSED) if (xutftowcs_path(wpath, path) < 0) return -1; ret = _wmkdir(wpath); + if (!ret) + process_phantom_symlinks(); if (!ret && needs_hiding(path)) return set_hidden_flag(wpath, 1); return ret; @@ -2723,6 +2850,42 @@ int symlink(const char *target, const char *link) errno = err_win_to_posix(GetLastError()); return -1; } + + /* convert to directory symlink if target exists */ + switch (process_phantom_symlink(wtarget, wlink)) { + case PHANTOM_SYMLINK_RETRY: { + /* if target doesn't exist, add to phantom symlinks list */ + wchar_t wfullpath[MAX_PATH]; + struct phantom_symlink_info *psi; + + /* convert to absolute path to be independent of cwd */ + len = GetFullPathNameW(wlink, MAX_PATH, wfullpath, NULL); + if (!len || len >= MAX_PATH) { + errno = err_win_to_posix(GetLastError()); + return -1; + } + + /* over-allocate and fill phantom_symlink_info structure */ + psi = xmalloc(sizeof(struct phantom_symlink_info) + + sizeof(wchar_t) * (len + wcslen(wtarget) + 2)); + psi->wlink = (wchar_t *)(psi + 1); + wcscpy(psi->wlink, wfullpath); + psi->wtarget = psi->wlink + len + 1; + wcscpy(psi->wtarget, wtarget); + + EnterCriticalSection(&phantom_symlinks_cs); + psi->next = phantom_symlinks; + phantom_symlinks = psi; + LeaveCriticalSection(&phantom_symlinks_cs); + break; + } + case PHANTOM_SYMLINK_DIRECTORY: + /* if we created a dir symlink, process other phantom symlinks */ + process_phantom_symlinks(); + break; + default: + break; + } return 0; } @@ -3424,6 +3587,7 @@ int wmain(int argc, const wchar_t **wargv) /* initialize critical section for waitpid pinfo_t list */ InitializeCriticalSection(&pinfo_cs); + InitializeCriticalSection(&phantom_symlinks_cs); /* set up default file mode and file modes for stdin/out/err */ _fmode = _O_BINARY; From 96b8760220bcc527ad528e245ae79d2b76463c97 Mon Sep 17 00:00:00 2001 From: Johannes Schindelin Date: Wed, 17 Dec 2025 14:08:53 +0000 Subject: [PATCH 16/18] mingw: try to create symlinks without elevated permissions As of Windows 10 Build 14972 in Developer Mode, a new flag is supported by `CreateSymbolicLink()` to create symbolic links even when running outside of an elevated session (which was previously required). This new flag is called `SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE` and has the numeric value 0x02. Previous Windows 10 versions will not understand that flag and return an `ERROR_INVALID_PARAMETER`, therefore we have to be careful to try passing that flag only when the build number indicates that it is supported. For more information about the new flag, see this blog post: https://blogs.windows.com/buildingapps/2016/12/02/symlinks-windows-10/ Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/compat/mingw.c b/compat/mingw.c index 59a32e454e..3e2110a87a 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -331,6 +331,8 @@ static const wchar_t *make_relative_to(const wchar_t *path, return out; } +static DWORD symlink_file_flags = 0, symlink_directory_flags = 1; + enum phantom_symlink_result { PHANTOM_SYMLINK_RETRY, PHANTOM_SYMLINK_DONE, @@ -381,7 +383,8 @@ process_phantom_symlink(const wchar_t *wtarget, const wchar_t *wlink) return PHANTOM_SYMLINK_DONE; /* otherwise recreate the symlink with directory flag */ - if (DeleteFileW(wlink) && CreateSymbolicLinkW(wlink, wtarget, 1)) + if (DeleteFileW(wlink) && + CreateSymbolicLinkW(wlink, wtarget, symlink_directory_flags)) return PHANTOM_SYMLINK_DIRECTORY; errno = err_win_to_posix(GetLastError()); @@ -2846,7 +2849,7 @@ int symlink(const char *target, const char *link) wtarget[len] = '\\'; /* create file symlink */ - if (!CreateSymbolicLinkW(wlink, wtarget, 0)) { + if (!CreateSymbolicLinkW(wlink, wtarget, symlink_file_flags)) { errno = err_win_to_posix(GetLastError()); return -1; } @@ -3523,6 +3526,24 @@ static void maybe_redirect_std_handles(void) GENERIC_WRITE, FILE_FLAG_NO_BUFFERING); } +static void adjust_symlink_flags(void) +{ + /* + * Starting with Windows 10 Build 14972, symbolic links can be created + * using CreateSymbolicLink() without elevation by passing the flag + * SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE (0x02) as last + * parameter, provided the Developer Mode has been enabled. Some + * earlier Windows versions complain about this flag with an + * ERROR_INVALID_PARAMETER, hence we have to test the build number + * specifically. + */ + if (GetVersion() >= 14972 << 16) { + symlink_file_flags |= 2; + symlink_directory_flags |= 2; + } + +} + #ifdef _MSC_VER #ifdef _DEBUG #include @@ -3558,6 +3579,7 @@ int wmain(int argc, const wchar_t **wargv) #endif maybe_redirect_std_handles(); + adjust_symlink_flags(); /* determine size of argv and environ conversion buffer */ maxlen = wcslen(wargv[0]); From 43152a227608d11e5e3cfe7e17f0b0988b4a0577 Mon Sep 17 00:00:00 2001 From: Johannes Schindelin Date: Wed, 17 Dec 2025 14:08:54 +0000 Subject: [PATCH 17/18] mingw: emulate `stat()` a little more faithfully When creating directories via `safe_create_leading_directories()`, we might encounter an already-existing directory which is not readable by the current user. To handle that situation, Git's code calls `stat()` to determine whether we're looking at a directory. In such a case, `CreateFile()` will fail, though, no matter what, and consequently `mingw_stat()` will fail, too. But POSIX semantics seem to still allow `stat()` to go forward. So let's call `mingw_lstat()` to the rescue if we fail to get a file handle due to denied permission in `mingw_stat()`, and fill the stat info that way. We need to be careful to not allow this to go forward in case that we're looking at a symbolic link: to resolve the link, we would still have to create a file handle, and we just found out that we cannot. Therefore, `stat()` still needs to fail with `EACCES` in that case. This fixes https://github.com/git-for-windows/git/issues/2531. Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/compat/mingw.c b/compat/mingw.c index 3e2110a87a..628a3941d2 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -1273,7 +1273,19 @@ int mingw_stat(const char *file_name, struct stat *buf) FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL); if (hnd == INVALID_HANDLE_VALUE) { - errno = err_win_to_posix(GetLastError()); + DWORD err = GetLastError(); + + if (err == ERROR_ACCESS_DENIED && + !mingw_lstat(file_name, buf) && + !S_ISLNK(buf->st_mode)) + /* + * POSIX semantics state to still try to fill + * information, even if permission is denied to create + * a file handle. + */ + return 0; + + errno = err_win_to_posix(err); return -1; } result = get_file_info_by_handle(hnd, buf); From 09c6a90daacc75b5eb03a9d7d9fcd4d3e67c582d Mon Sep 17 00:00:00 2001 From: Johannes Schindelin Date: Wed, 17 Dec 2025 14:08:55 +0000 Subject: [PATCH 18/18] mingw: special-case index entries for symlinks with buggy size In https://github.com/git-for-windows/git/pull/2637, we fixed a bug where symbolic links' target path sizes were recorded incorrectly in the index. The downside of this fix was that every user with tracked symbolic links in their checkouts would see them as modified in `git status`, but not in `git diff`, and only a `git add ` (or `git add -u`) would "fix" this. Let's do better than that: we can detect that situation and simply pretend that a symbolic link with a known bad size (or a size that just happens to be that bad size, a _very_ unlikely scenario because it would overflow our buffers due to the trailing NUL byte) means that it needs to be re-checked as if we had just checked it out. Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- read-cache.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/read-cache.c b/read-cache.c index 990d4ead0d..260f4b3b2f 100644 --- a/read-cache.c +++ b/read-cache.c @@ -470,6 +470,17 @@ int ie_modified(struct index_state *istate, * then we know it is. */ if ((changed & DATA_CHANGED) && +#ifdef GIT_WINDOWS_NATIVE + /* + * Work around Git for Windows v2.27.0 fixing a bug where symlinks' + * target path lengths were not read at all, and instead recorded + * as 4096: now, all symlinks would appear as modified. + * + * So let's just special-case symlinks with a target path length + * (i.e. `sd_size`) of 4096 and force them to be re-checked. + */ + (!S_ISLNK(st->st_mode) || ce->ce_stat_data.sd_size != MAX_PATH) && +#endif (S_ISGITLINK(ce->ce_mode) || ce->ce_stat_data.sd_size != 0)) return changed;